1. Field of the Invention
This invention relates to an apparatus for supplying a treatment liquid, such as a developer liquid, onto a substrate, such as a semiconductor wafer.
2. Description of the Related Art
U.S. Pat. No. 5,002,008 discloses a liquid supply apparatus of this type. In this apparatus, a liquid-supply nozzle is located above a rotatable spin chuck and opposed to a semiconductor wafer placed on the chuck. Drops of the developer liquid are applied onto the semiconductor wafer via through holes formed in the supply nozzle, and then the spin chuck is rotated, thereby spreading the developer liquid all over the wafer.
In the above apparatus, a holder or trench for receiving the supply nozzle when it is in a waiting state is provided at a side of the spin chuck. The holder generally consists of a box-like vessel for holding the supply nozzle with its through holes not sealed.
In the liquid supply apparatus constructed as above, the developer liquid may remain in the through holes when the nozzle is in the waiting state. The remaining liquid may deteriorate and solidify into particles. If the particles stick to the supply nozzle, the nozzle may not apply the developer liquid uniformly onto the wafer, or the particles may stick to the wafer.
To eliminate a developer liquid which degraded, a method for exhausting a predetermined amount of developer liquid from the holder, which is called "dummy dispensation", has been employed. This method, however, cannot eliminate the particles completely, and is not economical since it requires a great amount of developer liquid.